June 7th, 2008TAG+91 Binding Theory in LTAG Lucas Champollion University of Pennsylvania [email protected].

June 7th, 2008 TAG+9 1

Binding Theory in LTAG

Lucas Champollion

University of Pennsylvania

[email protected]

June 7th, 2008 TAG+9 2

Overview

Binding Theory (BT) and its local domains Previous work: Condition A This proposal: Conditions A, B, C Discussion

June 7th, 2008 TAG+9 3

Binding theory: A reminder Condition A: reflexives must be locally bound

Johnj thinks [ Billb likes himself*j / b / *[other] ]

Condition B: pronouns must be locally free Johnj thinks [ Billb likes himj / *b / [other] ]

Condition C: full noun phrases must be free *[ Johnj likes Johnj ]

*Johnj thinks [ Mary likes Johnj ]

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Binding theory in LTAG

LTAG’s local domain = the verbal elementary tree and its arguments (but not its adjuncts)

Insight from previous work: LTAG and BT have similar local domains

This presentation’s central point: Too many mismatches between local domains We can’t reuse LTAG’s local domain for binding!

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Previous work reused LTAG’s local domain

NP

loves

V NP

VP

S

himself

John

NP

V S*

VP

S

thinks

he

Condition A

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Previous work reused LTAG’s local domain

NP

loves

V NP

VP

S

himself

John

NP

V S*

VP

S

thinks

he

Condition A

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Previous work reused LTAG’s local domain

NP

loves

V NP

VP

S

himself

John

NP

V S*

VP

S

thinks

he

Condition A

June 7th, 2008 TAG+9 8

Previous work reused LTAG’s local domain

NP

loves

V NP

VP

S

him

John

NP

V S*

VP

S

thinks

he

Condition B

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Ryant and Scheffler (2006) Only Condition A MCTAG set with a

degenerate NP tree Tree-local MCTAG with

flexible composition makes sure that antecedent and reflexive substitute into the same tree

NP

loves

V NP

VP

S

himself

NPi

John

NP

NP*i{ }

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Kallmeyer and Romero (2007) Only Condition A MCTAG set with a

degenerate VP tree Tree-local MCTAG with

flexible composition makes sure that antecedent and reflexive substitute into the same tree

NP

loves

V NP

VP

S

himself

NPi

John

NP

VP*i{ }

(some features omitted)

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Kallmeyer and Romero’s claim

“Tree-local MCTAG display exactly the extended domain

of locality needed to account for the locality of anaphora binding in a natural way.”-- Kallmeyer and Romero (2007)

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A counterexample

VP*

opposite

P NP

PP

VP

himself

John

NP

V NP

VP

S

imagined

Cannot be handled by Kallmeyer and Romero (2007) except by flexible composition (which they try to avoid)

Bill

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ECM: another mismatch of localities

NP

to love

V NP

VP

S

Bill

John

NP

V S*

VP

S

expects

him

Can be handled with an extra feature No lexical ambiguity needed (unlike R&S 2006)

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Mismatches within Binding Theory

Bill

NP

NP

himself

NP

V NP

VP

S

found

John

NP

NP*

’s

Det NP

N’

NP

picture

N

P NP*

PP

NP

of

Bill

NP

NP

him

NP

V NP

VP

S

found

John

NP

NP*

’s

Det NP

N’

NP

picture

N

P NP*

PP

NP

of

Judgments tested experimentally (Keller and Asudeh ‘01; Runner ‘03)

AA BB

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Mismatches within Binding Theory

VP*

near

P

PP

VP

himselfJohn

NP

V NP

VP

S

saw a snake

NP

VP*

near

P

PP

VP

himJohn

NP

V NP

VP

S

saw a snake

NP

AA

BB

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How to encode the other conditions? Condition A roughly corresponds to tree-

locality Condition B = “enforced non-locality”? Condition C = ???

Need to propagate an unbounded number of potential antecedents

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This account in a nutshell Every NP receives three items from its

environment: a list “A” of local potential antecedents a list “B” of local potential antecedents a list “C” of nonlocal potential antecedents

Every NP supplies its own individual variable to its environment

The rest of the grammar is responsible for providing the correct lists to the NP substitution slots

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Technical innovation: List-valued features

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Elementary tree for “himself”(Condition A, simplified)

“A reflexive must be locally bound.”

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Elementary tree for “he”(Condition B)

“A pronoun must be locally free.”

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Elementary tree for “John” (Condition C)

“A full noun phrase must be free.”

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Sample derivation

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Sample derivation

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Sample derivation

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Sample derivation

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Condition C: the default case

Before...

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Condition C: the default case

...and after unification of top/bottom features

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Condition C across clauses

Before putting the trees together...

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Condition C across clauses

The higher tree passesits subject down, then...

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Condition C across clauses

...unification at the root node propagates the empty list

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Improvements over previous accounts...

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Binding into adjuncts

Just propagate everything!

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Mismatches between domains easily encoded Non-complementary binding conditions easily

handled with separate A and B list features No ad hoc trees needed for picture NPs (unlike

K&R ‘07)

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C-command violations easily encoded

No need for separate lexical entry Just extrapose subject NP along with its feature structure

(he)

(Himself)

e.g. extraposition: “Himselfi, hei likes.”

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Improvements at a glance

All conditions are implemented Higher empirical accuracy No lexical ambiguity No flexible composition (K&R 2007) No syntactically unmotivated degenerate

trees (Kallmeyer and Romero, 2008) Better integration with anaphora resolution

(Branco, 2002) No explicit representation of c-command

June 7th, 2008 TAG+9 36

Issues / Future work

Unknown complexity of list-valued features Just a decoration on the trees though -- they do

not rule out any sentences Lack of predictive power

How do we constrain possible feature values? Metagrammar?

Does TAG offer any insights into BT at all?

June 7th, 2008 TAG+9 37

Thank you.

Lucas Champollion

University of Pennsylvania

[email protected]

June 7th, 2008 TAG+9 38

Previous accounts do not interface well with anaphora resolution modules

Previous accounts: parser delivers a forest of indexed trees Johni introduced Billk to himselfi vs.

Johni introduced Billk to himselfk

Problem: Anaphora resolution modules are not prepared to compare entire trees (Branco, 2002)

Our solution outputs a compact set of constraints Following Branco (2002)

June 7th, 2008 TAG+9 39

The grammar of picture NPs

NP*

’s

Det NP

N’

NP

Bill

NP

NP

himself

NP

V NP

VP

S

found

picture

N

P NP*

PP

NP

of

John

NP

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Missing link problem

NP*

’s

Det NP

N’

NP

Bill

NP

NP

himself

NP

V NP

VP

S

found

picture

N

P NP*

PP

NP

of

John

NP